In collaboration with Professor Thomas Devlin of Hahnemann University in Philadelphia, PA an effort has been made to evaluate a prostaglandin derivative called PGBx for its protective action against ischemic brain damage. This compound, isolated in the course of studies on stress, was observed to protect vitro mitochondrial metabolism from hypoxia. Our interest rested on the opportunity to test the efficacy of PGBx in a model of cerebral ischemia which seemed definitive and relatively easy to assess. This model is the adult mongolian gerbil subjected to 15 minutes of bilaterial carotid occlusion. While untreated controls showed the expected 30% survivability at 7 days, over 92% of the treated gerbils survived. This beneficial result was present only if the PGBx was given 30 minutes after occlusion release followed by repeat doses at 1, 2 and 3 hrs. If given before or during occlusion or more than 1 hr after release from occlusion, the drug was essentially ineffective. As there are few drugs that offer benefit when administered after the ischemic injury, this drug appears to be deserving further study.